1. Field of the Invention
The invention generally relates to an irradiating device in the art of radiation processing, and a method for controlling the same.
2. Description of Related Art
Radiation processing is now used to prepare macromolecular materials, keep foods fresh, sterilize medical products and drugs, protect products from contaminating, color crystals and pearls, and treat environmental contaminants with high energy electron beams, X-ray generated by a target hit by electron beams or Gamma ray radiated by a radionuclide. The radiation processing, as an economic, energy saving, manpower saving and harmless new processing method, is widely applied to various fields such as agriculture, industry and medicine, and becomes increasingly important.
Generally, high energy electron beams are generated by accelerators such as traveling or standing wave linear accelerators, and DC high voltage accelerators, which further include static accelerators, transformer type accelerators with insulating core, electron curtain accelerators, high frequency and high voltage accelerators, etc. As shown in FIG. 1, an irradiating device outputting electron beams comprises an electron linear accelerator 1, a scanning magnet 3 mounted on the electron linear accelerator 1 via a flange 2, and a scanning box 4 of triangle shape. The scanning box 4 is provided with an electron beam exit window 10 right in a direction of electron beams output from the electron linear accelerator, and a cooling fluid loop 9 at the bottom of the scanning box 4 for cooling the electron beam exit window 10. The cooling fluid loop 9 is externally connected to a cooling fluid system via an inlet 8 and an outlet 12. In operation, the scanning magnet 3 scans in bidirectional mode, that is, a positive current and a negative scanning current are respectively supplied to the scanning magnet 3 for half of a scanning period. The irradiating device configured in this way typically directs electron beams 5 through scanning box 4, and then carries out radiation processing. Although radiation processing with electron beams has advantages of great power, high efficiency, excellent safety and so on, it could only be used for small or thin articles due to the low processing depth of electron beams. It is not suitable for processing big articles that cannot be separated into smaller ones, such as logs to be cleared of pests. Furthermore, the scanning boxes of the conventional electron beam exit window type irradiating devices are required to have scanning magnets with good stability. If the scanning magnet 3 fails in operation, even for a very short time, the electron beams 5 would damage the electron beam exit window 10 greatly, and even damage the entire system including the electron linear accelerator 1 and the scanning box 4.
Therefore, an irradiating device outputting X-rays is typically used to irradiate big articles that cannot be separated into smaller ones. As shown in FIG. 2, such irradiating device outputting X-rays comprises an electron linear accelerator 1, a shift section 13 mounted on the electron linear accelerator 1 via a flange 2, a target 7 mounted at a center of the outputting beams, and a cooling fluid loop 9 at bottom of the shift section 13 for cooling the target 7. The cooling fluid loop 9 is externally connected to a cooling fluid system via an inlet 8 and an outlet 12. The radiation processing is carried out utilizing X-rays generated by the target hit by the electron beams originated from the electron linear accelerator 1. X-rays can penetrate deeply, and thereby carry out radiation processing on bigger articles. However, its efficiency is lower than electron beams since X-rays are converted by electron beams impinging on the target.
In conventional accelerator irradiating devices, the radiation is implemented by either electron beams or X-rays generated by a target hit by electron beams. The articles suitable for being irradiated by these devices are limited.